1. Technical Field
The present invention relates to an apparatus for guiding a length of seat belt webbing relative to the body of a vehicle, and particularly to a D-ring assembly which guides a length of shoulder belt webbing in a vehicle.
2. Description of the Prior Art
In a typical three-point vehicle safety belt system, belt webbing extends from a retractor mounted on the vehicle body upwards through an opening in a D-ring fixed to the vehicle body. A shoulder belt portion of the webbing extends across a vehicle occupant's torso between the D-ring and a buckle assembly disposed inboard of the vehicle occupant seat. Upon vehicle deceleration at a rate above a predetermined rate, such as occurs in a collision, the shoulder belt webbing restrains forward movement of the vehicle occupant relative to the vehicle.
To restrain forward movement of the vehicle occupant, it is preferable that there be no slack in the shoulder belt webbing as it extends around the torso of the vehicle occupant. Thus, forward movement of the vehicle occupant would immediately be restrained by the shoulder belt webbing in the event of sudden vehicle deceleration such as occurs in a collision. However, some safety belt systems provide a small amount of slack in the shoulder belt webbing to increase the comfort level of the vehicle occupant. These safety belt systems allow some forward movement of the vehicle occupant to occur upon sudden vehicle deceleration and before the shoulder belt webbing restrains forward movement of the occupant. This can increase the risk or level of injury to the vehicle occupant.
It is known from U.K. published Pat. application 2243533A to move a D-ring upward on a vehicle upon sudden deceleration, to remove slack from ("pretension") the shoulder belt webbing.